Hackers may have breached U.S. government personnel records more than once, accessing data on employee background investigations, the White House said on Friday.

The breach was uncovered as authorities investigated the hacking of records on 4 million current and former federal workers maintained by the Office of Personnel Management, the government's human resources agency.

The latest hack may have affected "information related to the background investigations of current, former and prospective federal government employees," according to a White House statement.